In the field of endodontics, one of the most important and delicate procedures is that of cleaning or extirpating a diseased root canal to provide a properly dimensioned cavity while essentially maintaining the central axis of the canal for filling of the canal void and capping of the tooth. When done properly, this step enables substantially complete filling of the canal with biologically inert or restorative material without entrapping noxious tissue in the canal that could lead to failure of the therapy.
In a root canal procedure, the dentist removes diseased tissue and debris from the canal prior to filling the canal with a biologically inert or restorative filling material. In performing this procedure, the dentist must gain access to the entire canal, shaping it as appropriate. However, root canals often are very small in diameter, and they are sometimes quite curved. It is therefore often very difficult to gain access to the full length of the canal and to work all surfaces of the canal wall.
Many tools have been designed to perform the difficult task of cleaning and shaping root canals. Historically, dentists have used elongate, tapered endodontic files with helical cutting edges to remove the soft and hard material from within and adjacent the root canal area. These tools have generally been made by one of two basic processes. In one process, a file is created by twisting an elongate, tapered prismatic rod of either square or triangular cross section in order to create a file with one or more helical cutting/abrading edges (“K-file”). A second process involves grinding helical flutes into a circular or prismatic elongate, tapered rod to create a file with one or more helical cutting/abrading edges (“Hedstrom file”).
Conventional endodontic instruments with helical cutting/abrading edges have certain endemic problems which, to some degree, have been tolerated and approached from a management perspective rather than an elimination perspective. For example, conventional endodontic instruments are made of metal alloys and are rotated within a root canal during use. Cutting surfaces on the instruments remove, chip, and/or abrade material from the root canal as the instrument is rotated and/or reciprocated roto-axially. This rotational movement creates torsional and other stresses in the instrument body, which can cause a portion of an instrument to break off in the root canal when the instrument becomes over-torqued and/or fatigued. Additionally, as the instrument is moved roto-axially in the canal, the instrument may begin to screw into the wall of the canal, especially in curved sections, rather than continuing down the canal towards the apical tip of the root. In some cases, this “screwing in” can cause the instrument to break through the side of the root canal and into surrounding tissue or bone. Or, it may begin to “drift” or displace laterally relative to the center axis of the canal as it is moved roto-axially.
These and other problems continue to plague practitioners and designers alike in their efforts to enlarge and prepare for filling the varied tooth root canal configurations in a manner substantially concentric with the natural or original canal curvature/shape to enable successful, effective, and permanent treatment therapies.
Accordingly, there is a need for improved endodontic instrument designs and methods that will avoid, minimize, or eliminate drawbacks and problems associated with conventional endodontic instruments including, but not limited to, “screwing in” issues and lateral displacements encountered during use of conventional endodontic instruments.